The longest officially-released song, according to Guinness World Records, was composed and released by a Canadian artist named Earthena. "Symphony of the Crown" was released on October 1, 2021, and took a year to compose. It would also take quite a while to actually listen to the song — 48 hours, 39 minutes and 35 seconds, to be exact. If you're interested, the song is available on YouTube, in 25 parts, roughly two hours each. A cursory listen to various snippets reveals that the song is a mix — which can most charitably be described as "eclectic" — of jazz, electronica, and New Age music reminiscent of Mike Oldfield or Ray Lynch.
However, another song could theoretically shatter that record. As Classic FM notes, a German church has, for a few years now, been playing John Cage's song "As Slow As Possible" in the most literal possible sense, playing the piece over the course of 639 years. However, it's not clear if anyone is recording it, meaning that Earthena's record is likely to stand.
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